An account of the circle of ideas, results and techniques, which grew out of the study of Brownian motion and random obstacles. Divided into two sections, the t... » 

An account of the circle of ideas, results and techniques, which grew out of the study of Brownian motion and random obstacles. Divided into two sections, the text examines areas such as potential theory, eigenvalue estimates and developments in the field, and offers an overview of known results. «